Anisotropy of contact networks in granular media and its influence on mobilised internal friction

The anisotropy associated with the contact network in granular media is investigated. A unique expression for mobilised internal friction has been discovered using numerical simulations of monodisperse and polydisperse spherical assemblies under two-way cyclic axisymmetric and simple shear load paths. This uniqueness is described by a linear relationship between the macroscopic stress ratio and the geometric configuration of only the strong and non-sliding contacts, where strong contacts are those with a normal force magnitude greater than the mean normal force. A stress–force–fabric expression for arbitrary partitions of the contact network was derived analytically, providing a mathematical connection between the macroscopic state of stress and interparticle characteristics. Numerical simulations revealed that only strong and non-sliding contacts provided a non-zero contribution to the stress–force–fabric expression. Previous studies suggest the dominance of force anisotropy in the complete contact netwo...